Communications: electrical – Systems – Portable self-contained
Patent
1974-09-20
1976-08-24
Curtis, Marshall M.
Communications: electrical
Systems
Portable self-contained
235198, G06F 314
Patent
active
039769917
ABSTRACT:
A cathode ray tube caligraphic display system is described which automatically varies the beam intensity as a function of the writing or "stroke" rates to provide automatic brightness compensation as the symbol or vector write rates vary. The X and Y write rate signals are provided in digital form and converted to ramp voltages of varying slopes to "stroke" the line segments for the desired symbols, vectors or other indicia. The digital X and Y write rate signals are also applied to a Read Only Memory (ROM) which has brightness compensation data stored therein for various combinations of X and Y write rates. The digital signals representing the X and Y write rates function as addresses to the Read Only Memory to read out brightness compensation control signals to control the brightness of the symbol or other displayed object as a function of the write rates. For example, if the write rate increases, which would normally decrease the brightness of the symbol displayed on the cathode ray tube, the video signal applied to the cathode ray tube gun is increased to increase the beam intensity and maintain the brightness constant even though the write rate has increased. Similarly, a decrease in the write rate which would normally cause the intensity or brightness of the symbol, or object, to increase results in a video signal which reduces the brightness to maintain the overall brightness constant. In addition to controlling the brightness as a function of the write rates, provisions are made for modifying or controlling brightness as a function of the symbol size by simultaneously varying the write rates to adjust the symbol size and the beam intensity to maintain constant brightness even though the symbol size may be deliberately changed. In addition, yet another modification of the brightness control and compensation circuit contemplates suitable control of the cathode ray display when the brightness of any symbol or display is programmed to be different from that of the remaining symbol or displays.
REFERENCES:
patent: 3394367 (1968-07-01), Dye
patent: 3466645 (1969-09-01), Granberg et al.
patent: 3510865 (1970-05-01), Callahan et al.
Hickin Charles Wyndham Robinson
Smith David Allen
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